Tyres are made from rubber-based materials and compounds since their properties are an essential part of a tyre's job.
These properties change over time and may depend on a variety of factors to which the tyre is subjected throughout its useful life: weather, storage conditions, usage (load, speed, pressure…). The factors involved in wear are so variable that it is impossible to predict exactly how long a tyre will last.
Have your motorcycle/scooter tyres checked from time to time by a qualified professional in addition to your own regular checks.
After 5 years of use, have your tyres checked annually.
After 10 years of use, as a precationary measure, replace your tyres with new tyres even if they appear to be in a satisfactory state and even if they haven't reached the legal tread wear limit. This precautionary measure should also be applied to the air chambers and rubber accessories (rim strips...), except if the manufacturer indicates otherwise, as for the MICHELIN Bibmousse.